A brake pad of small and medium sized automobiles generally includes a steel back and a friction block, wherein the friction block is bonded and formed by friction materials such as an enhanced material, an adhesive, a filler and so on; and the steel back bears and supports the friction block and is stamped by and made of a steel board. When the automobile is braked, the steel back is pushed by a brake clamp, and its friction block contacts a brake disk or a brake drum and friction is produced; hence the objective that the automobile is decelerated or braked will be achieved through the friction. As a brake pad is the most critical part of a brake system of the automobile and plays a decisive role in the brake effect, the glued firmness between the steel back and a friction material and the strength of the steel back are the most important factor for the brake effect.
Currently, the steel back in the market is mainly divided into three types:
a burred steel back, wherein a proprietary CNC apparatus is adopted, and the surface of the steel back is burred; the broaching grooving of this steel back is lower in density, not firm enough and easy to be fallen down; meanwhile, the production efficiency of the steel back is low, and hence the steel back cannot be produced in mass;
a counter-bore steel back, wherein a certain number of counter-holes (blind holes) is punched on the surface of the steel back; when the steel back is bonded on a friction material, the friction material will move into the counter-bore (the blind holes), so as to increase the shear strength of the brake pad; however, the counter-bore (the blind holes) influences the appearance and flatness of a product during its process; and
a network locking steel back, wherein a steel mesh is directly welded on the steel back, so as to increase the shear strength between the steel back and a friction material to some extent; however, compared to the burred steel back, the shear strength of the network locking steel back is relatively low, and hence the network locking steel back can only be used within a specific range.
In WO 00/49308 A1, a brake plate and a method and an apparatus for manufacturing the brake plate are described.
The applicant has developed a steel back automatic broaching device (China invention patent CN101979200A). The broaching device can form a two-way broaching grooving on the steel back, with the advantages of fast and stable processing, a firm grooving root and high shear strength. However, as to the steel back automatic broaching device, the two-way broaching grooving shall be processed on the material of the same steel back for two times. That is, firstly, the broaching grooving in one direction shall be processed, and then the broaching grooving in the other direction shall be processed. Therefore, the processing efficiency shall yet be to be improved. Moreover, the processing method of the prior two-way broaching grooving is also easy to produce height difference, thus influencing the appearance and use performance of a product.